1. Field of the Invention
The present invention relates to a vitrified abrasive solid mass such as a vitrified grinding wheel or grindstone, which has a vitrified abrasive structure which includes abrasive grains and a vitrified bond for holding the abrasive grains together and which is reinforced by impregnation with a cured composition including a thermosetting synthetic resin and a surfactant. This invention is also concerned with a method suitable for manufacturing such a vitrified abrasive solid mass.
2. Discussion of the Related Art
An abrasive solid mass of vitrified bond type such as a vitrified grinding wheel or honing stick or bar uses a glassy bond or an inorganic bonding agent (a vitrified bond) for holding abrasive grains together so as to maintain a multiplicity of pores or voids within the vitrified abrasive structure. Owing to excellent properties of the vitrified abrasive solid mass, such as a relatively high degree of strength with which the vitrified bond holds the abrasive grains together, and a relatively easy dressing operation, the vitrified abrasive solid mass is widely used for precision grinding operations. There has been a need for an abrasive solid mass capable of performing a grinding operation with improved efficiency, to meet a recent demand for shortening of the required grinding time.
On the other hand, there has been proposed for practical use a vitrified abrasive solid mass wherein the proportion or content of the vitrified bond is made relatively high for increasing the grade of the vitrified abrasive structure, namely, for increasing the degree of strength with which the inorganic bonding agent holds the abrasive grains together. This vitrified abrasive solid mass has a higher hardness value, and can meet, to some extent, the above-indicated need for improving the grinding efficiency. However, this vitrified abrasive solid mass is not completely satisfactory. Namely, the use of the inorganic bonding agent in a relatively large proportion assures an increase in the grade of the vitrified abrasive structure, which contributes to an improvement in the grinding efficiency, but considerably reduces the porosity of the vitrified abrasive structure and results in difficult or insufficient fracturing and removal of the abrasive grains, leading to relatively easy glazing or clogging of the surface of the abrasive solid mass, relatively easy chipping of the structure, and other drawbacks encountered during use of the grinding tool. In addition, the use of the inorganic bonding agent in the relatively large proportion is likely to cause various drawbacks during the manufacture of the vitrified abrasive solid mass, such as cracking or deformation thereof and insufficient removal or burn-out of the primary binder of the inorganic bonding agent, in the firing process. The insufficient removal of the binder may cause the manufactured abrasive solid mass to have some amount of residual carbon.
Such a vitrified abrasive solid mass with reduced porosity may be manufactured by hot pressing of a mixture of the abrasive grains and the vitrified bond, and may be used for performing a highly efficient grinding operation. However, this manner of manufacturing the vitrified abrasive solid mass requires special manufacturing equipment which usually suffers from low manufacturing efficiency, leading to a relatively high cost of manufacture of the abrasive solid mass, and a significant limitation in the range of size of the abrasive solid mass that can be manufactured.